Cigarette smoking is an addiction with major health sequelae, exacting tremendous human and economic costs worldwide. Although significant progress has been achieved in recent years, effective pharmacologic and behavioral smoking cessation interventions remain limited. Preliminary data suggest that neurosteroids may represent novel agents for smoking cessation and play a protective role in stress-induced relapse. This project will hence evaluate neurosteroids (pregnenolone, DHEA, ganaxolone) and other promising candidates as adjunctive treatments to nicotine replacement therapy (NRT) in smoking cessation. Candidate treatments will be evaluated in a parallel-arm design. After one week of pre-cessation treatment with nicotine patch, 80 subjects who show an insufficient therapeutic response to NRT alone (using as an index the reduction in expired air carbon monoxide [CO], the same criterion as is used in Project 1: Clinical Trials (PD: Rose)) will be randomized to one of four conditions, comprising three candidate medications and a placebo control condition. Treatment will continue for one week pre-quit and 11 weeks post-quit. Using our proposed adaptive treatment model, NRT will be continued throughout the treatment period, and we will attempt to identify treatment interventions that will prove effective in augmenting NRT in smokers who do not respond adequately to NRT alone (approximately 80%). Nicotine dependence severity will be tracked using the FagerstrQm Test for Nicotine Dependence (FTND), and changes in ad lib smoking will be assessed by measuring expired air CO at weekly intervals pre-quit. Laboratory sessions pre-quit will be held at baseline, after the first week of NRT and after the second week of NRT plus selected agent. During each session, stress-induced craving and smoking behavior will also be assessed using the Paced Auditory Serial Addition Test (PASAT). After the three laboratory sessions conducted over the course of two weeks, participants will attempt to quit. Smoking and smoking abstinence will be assessed for 11 weeks after the quit date and at 6-month follow-up, and correlated with pre-cessation biological and behavioral markers (neurosteroid levels, stress-induced craving, expired air CO, others). These proof-of-concept findings will be used to guide the selection of treatments for more extensive evaluation in Project 1: Clinical Trials (PD: Rose).